1. Field of the Invention
The present invention relates to a navigation system using a recording medium and a recording and/or reproducing method for the navigation system. More particularly, the present invention relates to a navigation system for detecting, for example, the positional information of a vehicle, and a recording medium for recording such detected information.
2. Background of the Invention
Heretofore, in a navigation system to be mounted in a vehicle, map information recorded on a CD-ROM (compact disc read-only memory) consisting of an optical disc is read by an optical pick-up to display on a monitor. The monitor displays a map on which the present position of the vehicle and the like received from an artificial satellite are indicated.
Such a navigation system is disclosed by U.S. Pat. No. 4,571,684, for example.
However, in the navigation system of that type, since its CD-ROM disc is large in diameter, there is the problem that the reproducing unit for reading the recorded information on the CD-ROM becomes too large.
Because of this reason, it is necessary to install the reproducing unit in a location remote from the driver such as, for example, in the trunk or under the seat. This is very troublesome for the driver when he is required to replace the CD-ROM.
Moreover, since the CD-ROM is a recording medium for read-only operation, the user cannot record any data on the recording medium.
In contrast, a rewritable semiconductor memory can be used as a recording medium which can be recorded by the user.
However, there is a problem in that the amount of information which can be stored in the memory is limited. Also, there is another problem that when the user stores the user data in the memory contained in the system body, the data is stored in a manner unrelated to the CD-ROM. Therefore, it becomes difficult for the user to judge which data in the memory corresponds to which CD-ROM.
There is still another problem that in order to maintain the information stored in the semiconductor memory, a provision of a back-up power source becomes absolutely necessary. If the navigation system is to be mounted on a vehicle, there is the problem that the battery is wasted.
Besides the above, there is another conventional device in which user data of the navigation system is recorded on a card-like recording medium. However, this recording medium is not yet satisfactory in view of its recording capacity.
Furthermore, the device must be provided with both the playback unit of the CD-ROM and that of the card-like recording medium. There is, therefore, a problem in down-sizing of the entire system.